<!DOCTYPE html>
<script src="../../resources/testharness.js"></script>
<script src="../../resources/testharnessreport.js"></script>
Passes if it does not crash.
<script>
async_test(t => {
    if (window.internals) {
        var canvas = document.createElement('canvas');
        canvas.width = canvas.height = 300;
        var ctx = canvas.getContext('2d');
        document.body.appendChild(ctx.canvas);

        var offscreen = new OffscreenCanvas(300,300);
        var ctx = offscreen.getContext('2d');
        var img = offscreen.transferToImageBitmap();
        internals.forceLoseCanvasContext(canvas, "2d");
        ctx.createPattern(img, "repeat-y");
    }
    t.done();
});
</script>